service-proxy

Service-proxy is a reverse proxy server and client. The server is controlled by the client: clients connect to the server and register services and, thus, open ports on the server. The server then forwards traffic between these ports and the respective client ports.

           +--------+                         +--------+
           | Server |<---register services:---| Client |
           |        |    port x <-> u         |        |
           |        |    port y <-> v         |        |
           |        |                         |        |
Peer1 <--->[ port x ]<----forward traffic---->[ port u ]
PeerN <--->[ port y ]<----forward traffic---->[ port v ]
           |        |                         |        |
           +--------+                         +--------+

Usage

You can run service-proxy with the following command line arguments:

  -allowed-ips IPs
        set comma-separated list of IPs the server accepts
        service registrations from, e.g.:
        127.0.0.1,192.168.1.0/24 (default "0.0.0.0/0")
  -allowed-ports ports
        set comma-separated list of ports the server accepts
        in service registrations, e.g.:
        udp:2048-65000,tcp:8000 (default "udp:1024-65535,tcp:1024-65535")
  -c address
        start client and connect to address; requires -r
  -ca-certs files
        read accepted ca-certificates from comma-separated list of files,
        e.g., cert1.pem,cert2.pem,cert3.pem
  -cert file
        read this host's certificate from file, e.g., cert.pem
  -key file
        read the key of this host's certificate from file, e.g., key.pem
  -r services
        register comma-separated list of services on server,
        e.g., tcp:8000:80,udp:53000:53000
  -s address
        start server (default) and listen on address (default ":32323")

On a server, it is recommended to use certificates to authenticate clients (see -cert, -key, -ca-certs), to restrict the address to listen on and the addresses to accept connections from (see -s, -allowed-ips), and to restrict the ports that can be registered (see -allowed-ports).

Examples

Creating a certificate with IP address (SAN) for the server:

server$ openssl req -newkey rsa:4096 -new -nodes -x509 -days 3650 \
        -out server-cert.pem -keyout server-key.pem \
        -subj "/C=US/CN=server" -addext "subjectAltName = IP:192.168.1.1"

Creating a certificate for a client:

client$ openssl req -newkey rsa:4096 -new -nodes -x509 -days 3650 \
        -out client-cert.pem -keyout client-key.pem \
        -subj "/C=US/CN=client"

Running the server listening on IP address 192.168.1.1, in mTLS mode with certificate server-cert.pem and key server-key.pem, treating the client certificate client-cert.pem as a CA certificate, accepting connections from 192.168.1.0/24, and allowing TCP ports 32000-42000 for service registrations:

server$ service-proxy -s 192.168.1.1 \
        -cert server-cert.pem -key server-key.pem \
        -ca-certs client-cert.pem \
        -allowed-ips 192.168.1.0/24 -allowed-ports tcp:32000-42000

Running the client connecting to the server's IP address 192.168.1.1, in mTLS mode with certificate client-cert.pem and key client-key.pem, treating the certificate server-cert.pem as a CA certificate, and registering TCP ports 32000 and 32001 on the server with forwarding to port 32000 and 8080 on the client:

client$ service-proxy -c 192.168.1.1 \
        -cert client-cert.pem -key client-key.pem \
        -ca-certs server-cert.pem \
        -r tcp:32000:32000,tcp:32001:8080